Large-size journal or thrust bearings of this type are frequently made with a multiplicity of spacing units including sliding heads of elastically deformable low-friction material, preferably a synthetic resin such as nylon or Teflon, which are carried on one support member and extend across an intervening gap, centered on the axis of rotation, to a confronting contact surface of the other support member. In a journal bearing, the support members may be a pair of coaxial bearing rings; the outer support, however, might also be a larger structure, such as a wall or a base on which the shaft is rotatably mounted.
While the elasticity of the sliding heads facilitates their adaptation to the shape of the contact surface, the stresses due to the load and to the relative rotation tend to broaden the faces of these heads and also to extrude some of their material laterally into the gap. A partial solution to this problem resides in the provision of retaining sleeves surrounding the sliding heads, e.g. as described in U.S. Pat. No. 3,819,241 according to which the heads project radially beyond their retaining sleeves to an extent which corresponds to the elastic compressibility of the heads under load. Thus, upon loading, the sliding heads become flush with their retaining sleeves so that part of the load is borne by these rigid sleeves which thereby determine the minimum separation of the bearing rings anywhere along the gap. When under less than maximum load, the sliding heads rise above their sleeves so that portions thereof are unprotected and tend to creep sideways, especially when subjected to compressive forces in a direction other than perpendicular to the bearing axis. The exposed portions of the sliding heads are also liable to contamination by abraded particles and by atmospheric agents.